1. Field of the Invention
The present invention relates to a resistance type sensor suitable for detecting a force externally applied.
2. Description of Related Art
A resistance type sensor is generally used for converting into electrical signals the magnitude and direction of a force applied by an operator. For example, in an input device for a cellular phone, a resistance type sensor for inputting multidimensional operations is incorporated as a so-called joystick.
A general resistance type sensor can output an X-axial signal corresponding to an X-axial direction; and a Y-axial signal corresponding to a Y-axial direction, for example, as disclosed in JP-A-2004-37350. The resistance type sensor can detect a force applied to an operation button, by resolving the force into its X- and Y-axial components.
In the case of applying such a resistance type sensor to a joystick, however, it is preferable that the sensor can output not only an X-axial signal corresponding to the X-axis and a Y-axial signal corresponding to the Y-axis, but also a Z-axial signal corresponding to a Z-axis different from the X- and Y-axes. For example, in the case of applying the resistance type sensor to a joystick for moving a cursor on the basis of X- and Y-axial outputs, and performing a predetermined operation such as clicking on the basis of a Z-axial output, the cursor can be moved to a predetermined position, for example, on an icon, by changing the X- and Y-axial outputs, and then the predetermined operation can be performed by changing the Z-axial output.
In the resistance type sensor capable of outputting X-, Y-, and Z-axial signals, however, an X-axial signal corresponding to an X-axial force Fx, a Y-axial signal corresponding to a Y-axial force Fy, and a Z-axial signal corresponding to a Z-axial force Fz, may be always output when any force is applied to the operation button. Therefore, when only the X- or Y-axial output is intended to be changed, the Z-axial output may also change. On the other hand, when only the Z-axial output is intended to be changed, the X- or Y-axial output may also change.
Thus, in the case of applying the resistance type sensor to a joystick, when a force is applied for moving the cursor, the predetermined operation may be erroneously performed because not only the X- and Y-axial outputs but also the Z-axial output changes. On the other hand, when a force is applied for performing the predetermined operation, the cursor may be moved because not only the Z-axial output but also the X- and Y-axial outputs change. This makes it difficult to perform the predetermined operation with keeping the cursor at the predetermined position.